Yong-Pil Park

Vertical alignment of nematic liquid crystal by rubbing-free method on the SiC thin film layer

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of the silicon carbide (SiC) thin film. The SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability make SiC an attractive candidate for electronic applications. A vertical alignment of nematic liquid crystal by atomic beam exposure on the SiC thin film surface was achieved. The about 87° of stable pretilt angle was achieved at the range from 30 to 45° of incident angle. The good LC alignment is maintained by the atomic beam alignment method on the SiC thin film surface until annealing temperature of 300 °C. Consequently, the vertical alignment effect of liquid crystal and the good thermal stability by the atomic beam alignment method on the SiC thin film layer can be achieved.

Fabrication and optical evaluation of aspheric glass lenses for 3 megapixel zoom camera phone module

The purpose of this study is to develop aspheric glass lenses 4mm in diameter by compression molding. The lens is intended for use as an optical design of 3 megapixel and 2.5 magnifications zoom in a camera phone module. Because of the excellent optical performance of glass and aspheric element, which minimize optical aberrations, the adoption of optical designs using of aspheric glass lenses is rapidly increasing with the progress of precision image forming optics. We fabricated the mold using ultra-precision processing of tungsten carbide (WC). The aspheric glass lens was precisely molded and then its characteristics were evaluated. The mechanical and optical properties of the molded lens were investigated and it showed 90–95% transcription ratio and 0:0655λ root-mean-square optical path difference (OPD-rms), which corresponds to a 0.844 Strehl ratio. Based on the optical performance using the Marechal criterion, we supposed that the molded lens is suitable for the optical design. It also means our fabrication process is available.

Wound Healing Effect of 525 nm Green LED Irradiation on Skin Wounds of Male Sprague Dawley Rats

Many methods exist that promote wound healing, including light therapy, which consists of light beams that assist the human body in treating and sterilizing wounds, as well as regenerating cells. Irradiation with specific wavelengths of either laser or LED light has been shown to induce beneficial proliferation of fibroblasts that, depending on the size of the wound, can be effective in promoting wound healing. The experiments in this study utilized 8 week old 250~300 g Male Sprague Dawley Rats (ILAR Code: NTacSam:SD) and included a non-irradiation group and a 525 nm green LED irradiation group (n of each group

The Effect of LED Light Irradiation on Skin Injury Cure of Rat

We developed the 4-channel Light Medical Therapy Apparatus for Skin Injury Cure using a high brightness LED. This equipment was fabricated using a micro-controller and a high brightness LED, and designed to enable us to control light irradiation time, intensity and reservation. In this paper, the designed device was used to find out how high brightness LED light affects the skin injury of SD-Rat(Sprague-Dawley Rat). In the experiment, wounds on the skin injury of SD-Rat(Sprague-Dawley Rat) were made. Light irradiation group and none light irradiation group divided, each group was irradiated one hour a day for 14 days. In result, compared with none light irradiation group, the lower incidence of inflammation and faster recovery was shown in light irradiation group.

Analysis of ozone concentration for superconductor thin film

Abstract Ozone is usually generated from oxygen gas using a silent discharge apparatus and its concentration is less then 10 mol%. Ozone is condensed by the adsorption method, which is widely used for the growth of oxidation thin films such as superconductor. Highly condensed ozone is analyzed by three methods; ultraviolet absorption, thermal decomposition and Q-mass analyzing methods. Thermal decomposition method is most effective in the highly condensed ozone region and its method is superior to Q-mass analyzer for determining ozone concentration because of the simplicity of the method. The decomposition of condensed ozone takes place mainly on the inner surface of the vessel. Ozone concentration decreased to less then 50 mol% over a 8 h period.

Electrical Properties of a CuPc Field-Effect Transistor Using a UV/Ozone Treated and Untreated Substrate

An organic field-effect transistor (OFET) was fabricated using a copper phthalocyanine (CuPc) as the active layer on the silicon substrate. The CuPc FET device was configured as a top-contact type. The substrate temperature was room temperature. The CuPc thickness was 40 nm, and the channel length and channel width were 100 μm 3 mm, respectively. Typical current-voltage (I-V) characteristics of the CuPc FET were observed and subsequently compared to the UV/ozone treatment on substrate surface.

Characteristic Analysis of X-ray Device using the High Voltage Generator on Full-wave Rectification Method

X-ray system which is usefully used in diagnosis of the patient, being bombed of radioactivity is a big weak point when irradiates a X-ray to the human body so that ICRP restricted the radiation exposure tolerance of the human body. In order to reduce being bombed, the many research and development is now advanced. A lots of diagnostic X-ray machines have currently used due to the increase of occurrence efficiency of X-ray and precisely the output control by using the inverter which is a high speed switching semiconductors. For getting the confidence of the X-ray machine, the same radiation occurrence, same evaluation, and same irradiation condition are necessary when evaluates X-ray irradiation. It is the most important part for the accuracy of the test result and the patient safety. This research has produced the high voltage occurrence system of full-wave rectification method by using the LC resonance inverter, and evaluated the irradiation reproducibility in order to use it in diagnosis of the patient.

Study on image processing of panoramic X-ray using deviation improvement software

Utilization of panoramic X-ray device is getting wider. Panoramic X-ray has low resolution than general X-ray device and it occurs to distortion by deviation of image synthesis. Due to structural problems, it has been used restrictively to identify of tooth structure, not for whole head. Therefore, it designed and produced panoramic X-ray device which is possible to diagnostic coverage can be extended and had to be adjusted interval control between X-ray generator and image processing for whole of Maxillofacias diagnosis. Produced panoramic X-ray device is composed basically of short image synthesis. In addition, it was confirmed the results by used the device which was applied deviation of the brightness of the image, filter to improve the location of the deviation and interpolation method. In this study, it was used 13 images including the front. It occurs to brightness deviation, position deviation, and geometric correction when synthesis of image, but it had been solved by deviation improvement software and a change of CCD cameras scan line which is used for image acquisition. Therefore, it confirmed expansion possibility of utilization range to commonly used panoramic X-ray device.

The Study on the Mobile Diagnostic X-ray Device of Frequency Modulation Method by PI Controlled

Mobile X-ray device which is typically used in the mobile type of X-ray can be used very usefully beyond the space restriction. In this study, we had designed and produced the high capacity of mobile X-ray device which does not have the limitation on diagnostic areas of the body, and then we were identified the operating characteristics of device according to the load variations. Mobile X-ray device is used the high capacity condenser which gives light weight and high performance for produce the mobile X-ray device that does not have a limit the diagnosis of the human body without a separate area of the power plant. It was designed and manufactured the high voltage generator device which is applying the frequency modulation method that is known to be excellent of reduced the power consumption of high voltage occurrence and power factor. Therefore, we were confirmed the X-ray irradiation and change in frequency which are caused by load variations used by oscilloscope and exposure dose meter.

Liquid Crystal Alignment Properties on Zirconia Doped Polyimide Layer

This paper introduces zirconia (ZrO2) use in liquid crystal (LC) alignment for uniform and effective LC orientation. We used a conventional rubbing process to induce LC alignment. As a result, uniform LC alignments were achieved in all samples with ZrO2 nanoparticles from 0.01 wt% to 0.3 wt%. Pretilt angles of LCs on ZrO2 nanoparticles doped LC alignment layers slightly increased as the percentage of ZrO2 nanoparticles rose. However, contact angles were almost the same. When twist-nematic (TN) LC cells used LC alignment layers with ZrO2 nanoparticle content of 0.1 wt%, best performance was shown. Finally, it is shown that ZrO2 nanoparticles doped LC alignment layers have more thermal budget than pristine ones in thermal stability test.